In recent years, the Thin Film Transistor-LCD (TFT-LCD) has been rapidly developed and applied widely. For the TFT-LCD in the mainstream market, three types, which respectively are Twisted Nematic (TN), Super Twisted Nematic (STN), In-Plane Switching (IPS) and Vertical Alignment (VA) can be illustrated. The VA liquid crystal display possesses extremely high contrast than the liquid crystal displays of other types. It has very wide application in large scale display, such as television or etc.
The reason why the VA liquid crystal display possesses extremely high contrast is that the liquid crystal molecules are vertically aligned to the substrate surface, and no phase difference exists, and light leakage is very small, and the dark state brightness is extremely small at the dark state without applying electricity. The lower the brightness at the dark state can be, the higher the contrast is according to the contrast calculation formula. However, because the VA liquid crystal display utilizes vertical twist liquid crystals and the birefraction difference of the liquid crystal molecules is larger, the issue of the color shift under large view angle is more serious. For earning better wide view angle property for the VA liquid crystal display panel to improve the color shift issue, the multi-domain VA (MVA) technology is commonly utilized, which is to divide a sub pixel into many districts and drive the liquid crystals in respective districts to lie down toward different directions as applying voltage. Thus, the watch results from respective directions can be equal. There are many ways to achieve MVA technology. One of these ways is to process the ITO pixel electrode at one side to be a pozidriv pattern. With the special ITO pixel electrode pattern, the tilt electric field can induce the liquid crystal molecules in different areas to lie down toward different directions.
With the development of the technology, related improvement appears. The polymer-stabilized vertical alignment (PSVA) wide view angle technology can make the liquid crystal display panel possess advantages of faster response time and high transmittance. The distinguishing feature is to form polymer protrusions on the surface of the alignment film to make the liquid crystal molecules have a pre-tilted angle. The general PSVA pixel structure is to accomplish the passivation on the array substrate for protecting the channel, and then the pixel electrode deposed thereon is implemented with pattern process. As shown in FIG. 1 and FIG. 2, which is a PSVA liquid crystal display panel according to prior art, comprising an upper substrate 100 and a lower substrate 200. The upper substrate 100 comprises a first substrate 110 and a plane type common electrode 120. The lower substrate 200 comprises a second substrate 210, a passivation layer 220 and a pixel electrode 230. The pixel electrode 230 has a pozidriv pattern. However, the pixel electrode 230, which is processed to have the pozidriv pattern, forms pixel electrode branches and slits interval patterns extending toward different directions. It results in the nonuniform electrical field which is formed with the common electrode 120 of the upper substrate 110 corresponding thereto. The electrical field corresponding to the pixel electrode branch region is obviously stronger than the electrical field corresponding the silt region. Accordingly, the uneven brightness phenomenon happens in the pixel.
For solving the existing issues of the PSVA liquid crystal display panel according to prior art, a new PSVA liquid crystal display panel is proposed, which is to form patterns on the passivation layer to obtain a plurality of trenches, and then to cover the passivation layer entirely with the entire surface pixel electrode; in comparison with the PSVA liquid crystal display panel according to prior art, the PSVA liquid crystal display panel possesses advantages of high transmittance, insensitivity to the cell gap and Line/Space. However, the different trench depths result in different transmittances. There remain doubts about what kind of trench depth can make the liquid crystal display panel obtain the best optical performance, and this will bring uncertainty to the process tuning.